Picture reproducing apparatus



June 8, 1937. H. SHORE ET AL PICTURE REFRODUCING APPARATUS Filed Aug. 22, 1931 4 Sheets-Sheet 1 HENRY SHORE & JAM 5 Q1. WHITAKER BY v um 'ATTO NEY J une 8, 1937. H..SHORE ET AL ,083,245

PICTU RE REPRODUC ING APPARATUS Filed Aug. 22, 1931 4 Sheets-Sheet 2 Bi El 5 Ann IIHIIIHIHI YYYY SQUBJECT svucuaomzzo LINE TONE SCREEN TONE O5C|LLATOR AMPLIFIER RECTIIYIER CONVERTER i g I June 8, 1937.

H. SHORE ET AL PICTURE REPRODUCING APPARATUS Filed Aug. 22, 1931 4 Sheets-Sheet 3 INVENTOR HENRY SHORE JAMES M. WHI AKER BY W, ATTO EY Patented Juno 8, 1937 UNITED STAT as PATENT OFFICE morons anrnopuonvo APPARATUS Henry Shore. Elizabeth. N. J.. and James N. Whitaker, Tuckahoe, N. Y., assignors to Radio Corporation of America. a corporation of Dela- Application August 22.

18 Claims.

The present invention relates to a. method and apparatus-for transmitting intelligence, which is preferably -in the form of a picture record, to a remote point where an eiectro-optical image or likeness of the transmitted subject is to be reproduced. .Broadly speaking, the invention is one which is capable of transmitting any type of intelligence but is particularly directed to the transmission of subjects which can be observed by the eye. These subjects, for example, may be pictures, copies of newspapers, financial statoments, film records. such as motion picture film with or without sound accompaniment, fashion plates, copies of finger prints. drawings, or other 1 similar matter.

Broadly speaking, the invention will herein be characterized as a constant frequency variable dot system by the use of which printed subject matter or the like may be transformed into a series of electrical impulses which, when received over a radio or a wire line communication channel. may be utilized for reproduction pur-' poses. The constant frequency variable dot system of transmission consists essentially in. the conversion of amplitude changes of a carrier or tone frequency into varying weight signalling or marking impulses which are transmitted at constant frequency and amplitude so that the useful period-of transmission, which will at the rcecivintensity of light and shadow on the subject varies between middle grayand black for example, the type of marking to reproduce these particular tonal values of the subject changes ,to a

marking of variable duration with equal spacing between each marking representation. With the type of marking now used to denote the lighter portions of the picture, the relationship between the marking and spacing periods may vary from [equality of marking and spacingpcriods to as to fifty time: the time durationof thespacing immueh as fifty times the time duration of spacing to the, time duration of marking. whereas" forthe darker portions of the record the time duraticn of.....the marking impulses with respect to the spacing impulses may vary from equality to 1981, Sei'lal No. 558,750

pulses. Thus, it is seen that, in addition to varying weights of marking impulses, the frequency at which these impulses are transmitted is varying and with the usual type of equipment now in use for transmitting records of this type this variation in frequency range may be, for example, 7

between'fifty and three hundred and fifty cycles per second.-

According to the present inventionyit is desired to transmit signals which will be reproduced as marking impulses always at a constant fre- .quoncy, so that the number of marking impulses g per unit of time is constant, that is, the sum of the marking and spacing duration for any value of density is' always constant but the marking duration depends upon the density of the sub: jeot at the point of scanning. Suppose, for example. that it is desired to transmit one hundred and fifty dots per second and for a light portion of the subject the marking interval might be 1/1500 of a second. then 'it'is seen that the spacing duration would be 0/ 1500 of a second. However, for a dark portion of the record the conditions might be such that the marking pulses occur for 7/1500 of-a second whereasthe spacingwas reduced to 3/1500 of a second.- In both of these cases it would be noted however that the sum of the marking and spacing time periods is always 1/150 of a second, or if the one'hundred V and fifty dots per second first assumed is the screen frequency, than it is seen that the sum oi the marklng'and spacing impulses per time unit is always the reciprocal of the screen fre quency.

This'syste'm of transmissioneirerts less strain upon the radio transmitter than the system previously used. since the required range of har monies of the keying frequency is reduced. This applies to the radio receiver as well.

The theory of operation upon which a syste of the type to be hereinafter disclosed is predicatecl may be given substantially as follows: The

output of the scanning head. which includes the usual photoelectric element for converting the variable intensities of light and shadow on different and successive elemental sections of the picture record for transmission into corresponding or proportionate electric current impulses and which light from the'picture as it influences the photoelectric element is interrupted at a predetermined rate, for example 3500 cycles. to introduce a tone carrier into the output of the --photocloctric element. will;bean amplitude modulated carrier of the tone frequency. It is to be understood, however, that any suitable form of u apparatus for producing the tone frequency may be used, for example, a bridge arrangement may be supplied wherein there are two or more tubes to which a tone frequency is fed 'and across which the tone frequency may be taken out. In such an arrangement the photo cell is connected across one diagonal of the bridge arrangement and as the cell becomes illuminated, or darkened, it serves to unbalance the bridge. Another system for producing the tone frequency may be provided by using what is known as the modulated type of scanning device wherein the carrier tone frequency is coupled to the input of the photo cell amplifier tube, In such a system, forming a portion of the tube input circuit, there is a resistor element series-connected between the amplifler tube filament and the grid, and across the resistor the photo cell and its battery are connected, so that if the amplifier tube is arranged to operate near the cut-off point the variations in illumination upon the photocell produces a variation of bias on the grid of the amplifier tube which changes the amplified current output thereof.

This amplitude modulated output energy is at 'a relatively low signal level which must then be amplified to be put to any useful purpose. After the picture modulated photo cell current is properly amplified, the resulting amplitude modulated tone frequency carrier is then rectified and the rectifier output resistor is made sufliciently transmission is carried-upon a record holder or drum' which is driven from any suitable form of motor and with the present system, in addition to driving the picture record holder, provision is made for rotating a tone generator, the output of which is arranged to .be fed into the mixing tube along with the rectified picture signal.

However, by the present system as proposed, the mixing tube is preferably so biased that the screen tone does not actuate the grid-throughout its entire cycle, that is, the output of the rectifier when scanning a white portion of the picture blocks completely the screen tone from passing through, whereas a medium gray will permit but half of each cycle to get through, and a .black will permit the complete cycle to actuate the grid. The square wave amplifier which is energized from the output of the mixing tube is arranged so as to convert this output energy into constant amplitude pulses. of varying width, the width, of course, depending uponthe amplitude of the mixing tube output. The impulses appeering in the output of the square wave amplifier may then be used to key, a tone or carrier,

. frequency. The resultant tone or carrier frequency signal is then .placed upon a transmission line orchannel suitable for keying a radio transmitter or a wire line distribution system.

From the above analysis. of the system and brief description of the functioning thereof, it is v seen that the type of picture which will result from such an arrangement resembles variable width recording which, while it gives a very presentable representation when held some distance away from the eye, gives a loss in detail when inspected closely. To overcome this difiiculty, a phase shift of 180 degrees of the screen tone is introduced on alternate traversals of the picture subject by the scanning element. This reversal produces at the receiving point a picture which closely resembles a half tone or which is more pleasingtothe eye and which will preserve the detail of the original subject for transmission. In this way, the system is arranged to produce a screen structure'which resembles the photographic half tone process while accomplishing results electrically. However. it should be noted that for black and white transmission, the screen frequency need not be used, nor need the double setting be used, but even with this type of transmission the use of the converter unit is advantageous due to the inclusion therein of the square wave amplifier.

From the brief and general statement above of the principles of operation of the invention, it will be seen that we have sought, as a primary object of the invention, to develop a system in which improved quality of the received records is obtainable. I

A further object of the system is to provide a system which is easy to maintain and to operate and which will function at increased working speeds.

sun 9. further object of the invention is to eliminate from the transmission of record subjects substantially the entire personal element.

This is made possible by eliminating completely all biasing batteries. The elimination of all of the biasing batteries tends to reduce maintenance cost and, at the same time, tends to maintain the apparatus always in a condition ready to work without the necessity of making a series of preliminary adjustments where the circuit has been idle for a considerable period of time as would be the case where batteries or the like are used in the system.

A further object of our invention is to provide a system for converting the varying intensities of light and shadow of the elemental sections of a record subject into proportionate, strength electric current impulses and to adapt the system to high speed keying in a manner which will hereinafter become apparent.

Further obiects of the invention are to provide for .accuricy and stability of operation while maintaining a relatively simple and. fool-proof arrangement of circuits capable of transmitting electric current impulses which may be re-converted into a recording of increased detail and accuracy.

Still other and further obiects of the invention will suggest themselves and become apparent to those skilled in the art to which .the invention relates by making reference to the accompanying drawings, wherein:

Fig. '1 illustrates conventionally one form of circuit arrangement for providing the transmission facilities but omitting from the showing the tone generation and the initial conversion of the picture record intensities into electric current impulses; p v Fig.- 2 is a diagrammatical showing to represent the sequence of the various-'operationein the device; I

Pig. 3 represents a form of record adapted to system disclosed in Fig. 1. In Fig. 3 the portion it represents, reading from left to right, the

' change from white to black and back to white for four successive lines of recording, while portion b represents the same change in intensity but modifies the showing of Fig. So by providing a double setting whereby alternate lines of the recording' are displaced by one hundred and eighty electrical degrees, or, in other words, the marking of alternate lines takes place half way between each of the markings of the preceding and following line; v

Fig. 4 represents a suitable means for producing the double setting or phase shift to change the marking characteristics of the system from the form shown by Fig. 3a to that shown by Fig. 3b; and

Fig. 5 is a diagrammatic showing of a suitable form of receiving device for receiving picture signals transmitted by the system shown in Fig. 1. Figure 5 indicates a receiving system of the diversity type as controlling the recording in the photoradio recorder unit. which is to be understood as including either photographic or visual recording.

Now. to make reference to the drawings, and first to refer to Fig. 2 thereof, a subject for transmission has been illustrated as consisting of a record strip varying in intensity from left to right I from white to black. This record or subject.

when an elcctro-optical image representation is to be transmitted. is placed upon a record holder or support of any suitable design and character. The successive elemental areas of the subject are assumed to be exposed to illumination which. when it affects the photoelectric light converting element, will produce corresponding or proportionate changes in the output current from the cell. the greatest current. of course. being obtainable from high lights on the picture due to a maximum transmission of light through the picture or reflection of light from the picture.

and the minimum output occurring with black due to the fact that the light is blocked from passing through the picture or absorbed so as to prevent reflection from the picture. depending, of course, upon whether direct or indirect illumination is resorted to.

In well known manner. the amplitude controlled picturo frequencies occurrlng'at a rate corresponding to the rate of interruption of the light directed toward the photo cell are amplifled, after which they may be rectified and supplied to a converter unit which comprises a mixing tube and a square wave amplifier. Jointly with the application of the amplitude controlled picture frequencies being brought upon the converter, a synchronized screen tonerof a frequency depending upon the detail desired is supplied to the converter. and the resulting output from the square wave amplifier forming a portion of the converter is then directedto a line tone carrier frequency in the form of a modulator tube or tubes to which is also supplied the line tone carrier frequency. For line transmission work this personic frequency,. and for direct radio transmission the line tone oscillator may be of a radio frequency. The lower portion of Fig; 2 shows at a the varying amplitude picture frequency occurring in the output fromthe amplifier as varied bychanging from white to black on the, .picture subject. and it will be noted that the am-. plitude of the tone frequency is dsoreasing 'continuously. The portion 1) immediately below the diagrammatic showing of the rectifier indicates the envelope of the rectified output showinga continually decreasing amplitude pulse. Portion c of Fig. 2 shows the output from the square wave amplifier portion of the converter unit and depending upon the amplitude of the rectified signal the duration of the marking, as indentified by the portions m, n. etc., is determined. These converter outputs of constant amplitude but variable duration then serve to key the oscillator frequency which is transmitted as an interrupted carrier of constant amplitude but variable time duration depending-upon the marking. The resultant marking is shown by Fig. 3 where the successive lines reading'from leftto right are produced as impulses of yarying'width but occurring at constant frequency so that the recording takes place along successive vertical lines, as shown by Fig. 3 of the drawings. 80 arranged, light portions of the record will be produced merely as a dot, whereas for middle grays the dot is elongated into a rather short line and the spacing between successive markings is substantially equal, while for the black portions there is substantially no spacing between the markings which appear to occur for the entire available time period with the result that the marking is substantially continuous, as shown by the right hand portion 1' of Fig. 2, where the carrier or line tone oscillator frequency appears to be uninterrupted for a considerable length of time.

To refer now specifically to Fig.1 of the drawings. showing a preferred system and circuit for accomplishing the results above outlined with respect to Fig. 2 and portion a of Fig.8. the screen tone frequency, as generated in accordance with the arrangement of Fig. 4, for example, is applied to the terminals l and 3 from which this energy is directed by means of conductors B and I to'the primary winding 9 of a transformer ii and then transferred to the secondary winding it of the transformer to the input circuit of the vacuum tube It including input electrode ii. The output energy from the vacuum tube It is directed to the primary winding IQ of a transformer II from which it is transferred by means .of the secondary winding 23 to a potentiometer 25. By means of the adjustable contact 21 of the potentiometer the screen tone as now amplified by the amplifier I1 is supplied with desired amplitude strength to the input electrode 28 of the mixing .tube Ii. the potentiometer thus controls the bias on tube Ii in accordance with the setting of the adjustable contact 21. Plate potential for the amplifier i1 is supplied through a conductor connected at one end to one terminal of the primary winding ll of the transformer 2i and connected at the other end to a resistor 20 to regulate the plate voltage. The plate voltage is supplied from a tcrmirligl point fl to resistor 20 and thus to tube- Simultaneously with the application of the screen tone to-the amplifier ll, the input signals coming from the photo-eell-amplifier, which are in the form of variable amplitude signals of oon-' stant frequency, the frequency being dependent upon the chopper frequency (not shown) infiuencing the photo cell, are supplied to the terminals 1i and 8! from which they are directed by means of conductors Il and II to a potentiometer 4|. These fluctuating picture record sisnals may be controlled as totheir effective amplitude bymeans of the adjustable potentiometer 7g 55 and shunt-connected capacity elements 51,

grounded at- 50, which in turn connect with a conductor i leading to the terminal point 26. The output energy from the amplifier 40 is fed through the primary winding 50 of transformer 55 from the secondary 51 of which the amplified energy is directed to the vacuum tubes 50, 1| serving together as full wave rectifiers. The tubes 00 and H are ofthe usual alternating current type having their grid-and plate elements 1 0, 15 and respectively tied together. This connection is to avoid any directconnection as would be present with the usual type of fullwave rectifying tubes in common use. Across the output of the rectifier unit comprising the tubes 50 and 1| is shunt resistor 11 and in series with the output are inductance elements 19, 10 shunted by capacities 8|, 8|. Across the entire output from the rectifier combination is a resistor 00 and potentiometer 05. From the variable contact of the potentiometer a conductor 81 connects the resulting rectified picture signal input with the potentiometer 25, and by means of the adiustable contact this amplified and rectified picture signal input is supplied jointly with the screen tone" to the mixing tube 0| in such a manner as to control the period when the screen tone renders the amplifier 0| operative in accordance with the tonal value of the picture as represented by the signal supplied from the rectifier.

" The plate element 0| of the mixing tube H is supplied with plate potential through resistors 00, 05, 01, 05 and III which are connected with the terminal 05 serving as the source of plate potential supply. Connected with the output circult of the mixing tube 0| are the tubes I05 and H0 serving together as a square wave amplifier trait. The grid element In of the first tube I05 9! the square wave amplifier is energized-in accordance with the output signal fiowing from he mixing tube 0|.

As was explained .in the U. 8. Patent No. ,005,ll1 issued to Henry Shore, issued June 18. 005, and entitled "Amplifier", the output current from the first tube I05 of the square wave lifier flows in the circuit from the plate element I01 through the resistor element I00 to the source 05 of plate potential for the tube I05 then back to cathode in the usual manner. accordance withthe strength of current howin: in the tube I05, varying voltage drops are produced in the resistor I00. These varying Voltage drops, in turn, control the potential on the grid element III of the second tube H0 01' the square wave amplifier which is tied directly to one end terminal of the resistor element I00. With a heavy current passing through the tube I05 it is seen that there will be a substantial voltage drop occurring in. the resistor I00 with aosasss v ried positive with respect'to its previous potential so that the grid element III of the second tube II3 of the square waveamplifier tends to assume a potential positive with respect to the potential acquired for a maximum current flow through the first tube of the square wave amplifier unit. This causes the second tube IIO to commence to draw plate current so that. by means of the connection IIO from the plate element II5 of the second tube IIO through the capacity I2I which is tied to the grid I00 of the first tube I05 of the square wave amplifier unit, each increase in plate current strength flowing through the tube IIO tends to decrease, at a rate more rapid than normal, the current flow-through the first tube I05 oi the unit so as to bias the first tube substantially to cut-oil. irrespective of the rate at which the signal intensity supplied to the first tube decreases. The second tube II3 of the square wave amplifier unit draws its through a second resistor IN to the source of plate potential supply connected to the terminal 25.

In order to determine the character of the signal forming the useful output from the square wave amplifier unit a switch I21, which has terfrom either the first tube I05 or'the second tube IIO of the square wave amp1lfier,' depending upon whether the switch arm I21 rests against the lower or upper switch contact point. The output energy thus controlled is directed from the switch arm I21 through a conductor I20 to a second switch I3I which is normally resting against the right hand contact point, looking at Fig. l. The switch IOI connects through aconductor I01 to the midpoint of the secondary winding I00 of the transformer I to energize in a substantially cophasal manner the grids I10 and I11 of the push-pull connected tubes I10 and IOI which form a part of the line tone keying unit.

The line tone oscillator tube I40 is provided with the usual electrode elements comprising a plate element I44, a grid element I50, and the usual electron source or cathode. The plate element I44 of the oscillator tube I40 is connected with a capacity element I45 which in turn connects through resistor element I41 and an inductance I40 to thegrid element I50. Plate potential is supplied to the oscillator tube I40 through a choke I50 connecting through a resistor I51 with the source or plate potential connected with the plate potential supply terminal 25. shunting the inductance element I40 is a capacity element I55, in shunt with which is also a second capacity I51 which may be connected in circuit with the oscillatory circuit, comprising the inductance I40 and capacity I 55, by closing the switch I50. Any closure of the switch element I50 to connect the second capacity in shunt with the first capacity will, of course, change the natural frequency of operation, as is desirable under certain conditions where it is necessary to change the line tone frequency. Also connected across the grid circuit of the oscillator tube I40 is another capacity element III which connects at one end to the filament of the tube I40 and at the other end adiustably to a poll on the Inductance element [40, which point is grounded at I10. The output from the oscillator tube I40 is fed through a resistor III and potentiometer I50 to the primary. winding I00 of the transformer I4I. Prior to supplying the oscillatory energy to the transformer I, the strength- I81 to the primary winding I88 of the transsigned as to cause the picture signals to produce former I. As the oscillator frequency and the output signal from the square wave amplifier unit are simultaneously impressed upon the pushpull amplifying tubes I18 and IN, the oscillator frequency appears in the output windings I81 and I88 of the push-pull unit as a constant amplitude interrupted signal, the interruptions being produced in accordance with the output signal from the square wave amplifier unit, since, of course, the square wave amplifier signal does not modulate the carrier or tone frequency of the oscillator I48 in the push-pull unit but, because of the fact thatthis signal is supplied in such a manner as to appear substantially cophasally upon each of the grid elements I18 and I11, biases the push-pull tubes either to pass or block the oscillator frequency.

The useful output from the push-pull amplifler unit is transferred from the primary winding I88 of the transformer I88 through the secondary winding I88 which connects by way of conductors I88 and I81 to the terminals I88 and 28I which function as 'the output terminals either to the connecting line for line transmission or to the radio transmitter for radio transmission. In order to monitor the signal appearing in the output circuit of the push-pull amplifier unit, provision has been made by way of the transiormer I88 for the primary winding I81 to feed energy into the secondary I8I, and by inserting a suitable plug into the switch contact 288 the resulting output which is being directed to the line by way of terminals I88 and 211i may be determined.

In order to key the system by hand where hand keying is desirable, provision has been made by way of terminals 2 and.2i1 to energize the relay 228 by way of the winding 2I8 so as to cause the relay 228 to close. and, by moving the switch "I to the left hand position from that shown, the hand-keyed signal may be arranged to control the output from the push-pull unit comprising the tubes I18 and I8I.

In the circuit with the plate energy supply for the various tubes, provision is made for filtering and smoothing the plate energy supply by way of series-connected inductance elements 208 and shunt-connected capacities 281 which are grounded at 2. Each of the filament circuits connects at terminals H8 and 2| 8 with the source of heating current and, as shown, all tubes are of the indirectly heated type. although it is to be understood that other type tubes may be substituted where desired.

From the above description. it is believed it will become apparent that the system is so deconstant frequency variable duration marking impulses which when reproduced at the point of reception will produce the general type of mark-. ing shown by Fig. 3a. of course, it is to be understood that in any system of the type herein iliselosed it is impossible to represent the exact ype of markings which are produced by any hand-made drawing since the particular type of recording depends solely. upon the characteristics of the controlling circuits and the marking instrumentality, or, in other words, any system of the type herein disclosed is predicated upon such a theory that the method and apparatus disclosed will produce only the type of markings characteristic of the system, varied, of course, in

accordance with tonal variations of the subject for transmission, and that the particular type of markings can be produced only by a system of the same nature. Therefore, while effort has been made to illustrate graphically the type of markings produced bythe system, it nevertheless should be noted that such type of marking cannot be considered as a true and exact example oi the quality of transmission obtainable but merely I marking representations for the previous phase 2'5 position ofthe screen frequency. Such an arrangement of shifting the phase of the screen frequency can be accomplished conveniently by an arrangement of the general type shown by Fig. 4. By this figure, the tone wheels 288 and 281 which are driven from the driving means for rotating the picture record carrier are shown as provided with pick-up units 289 and 24I com-' prising a. magnetic core 248 about which is placed a suitable winding 248 and 241 connected with conductors 248, 28I and 288, 288 leading to switches 281 and 288 which in turn connect by conductors 28i, 288 through the double-pole double-throw switch 288 with the output line directed to the terminals i and 8 of Fig. 1. By Fig. 4 only two separate pick-up units and tone wheel generators for generating the screen frequency are shown, although it is to be understood that any suitable number of such generators, such as flve or ten with suitable connecting switches, may be provided where it is desired to have a wide range of flexibility in the system. In such case, each tone generator will be connected through a separate switch element, similar to that shown for the two tone wheel units to the connecting lines which lead to the output terminals I and 8.

Mounted upon the record'carrier is a cam unit 281 which, if the scanning unit is one which rotates continuously and is arranged to provide a relatively slow longitudinal movement between the pick-up unit and the carrier, may be driven at a speed equal to half the speed of the record carrier, so that at the completion of each single rotation of the record carrier drum the switch element 288 may be closed by the cam. If the scanning and reproducing systems are. of the reciprocating rather than the rotary type, so that the scanning unit moves at a relatively fast rate longitudinally'cf the record and at a'relatively slow rate across the record carrier, then the cam element may be made to close the switch at the end of one stroke and to open the switch at the end of the stroke in the opposite direction. Connected to the terminals of the double setting unit. such as double-pole double-throw switch 288, ac-

tuated by the closure of the switch 288 by the position of the double-pole double-throw relay switch 285 connected with the conductors 28l, 283 leading from thepick-up units. The middle two terminals of the double-pole double-throw relay switch connect with the output lines leading to the terminals i and 8, whereas the outside terminals connect in reverse order with the conductors leading to the-pick-u'p units and upon the position of the double-pole double-throw relay depends the direction of current fiow through the conductors to the terminals l and 3. Therefore, at the end of each separate line of recording for each of the series of elemental areas or sections forming each line of the picture record the phase of the screen tone frequency is shifted by one hundred and eighty degrees, and thus the input frequency to the amplifier tube I5 is shifted. Consequently, the entire operation of the system comprising the converter unit in the form of the mixing tube and the square wave amplifier is reversed, so that the type of marking produced is changed from that shown by Fig. 3a, with no double setting, to that shown by Fig. 3b with double setting. This double setting feature, it will be seen, improves the detail of the picture to a considerable degree and provides an arrangement for resembling in the received record the usual half-tone print.

It is to be understood, of course, that while we have shown one suitable form of device for accomplishing the double setting, the invention is not restricted to the particular form shown but other suitable forms of arrangements for producing the effect of double setting may be used where desired, and the particular form of device shown is merely illustrated to complete the combination.

As disclosed by Fig. 5 of the drawings, a system for receiving the signals transmitted from the output of the arrangement show by Fig. 1 may, for example, in the case of radio reception, consist of a plurality of spaced antenna systems 215, 211 and 219. These antennae are geographically separated so as to permit diversity reception in order to avoid. the detrimental eifects of fading and the like, as has been taught by Beverage and Peterson, for example in their U. S. Letters Patent, No. 1,874,866 issued August 30, 1932 and entitled Method and means for eliminating fading on short wave lengths. Each antenna system is connected to a radio .frequency amplifier which feeds its output into a detector stagefrom which the received energy is directed through an audio frequency amplifier and rectifier unit. Each of the rectifier units as receiving energy from the three separated antenna systems is arranged to feed the output energy .in common across the first tube of a combining unit whichis so arranged that the plate current flowing through the combining unit, as controlled by the rectified receiyed signals in the combining unit 28l, may be made to control or key a tone keyer 288. The tone frequency generated in the tone generator 285 is directed to the tone keyer unit 283, which includes a-pushpull stage with the grids'controlled as to potential by means of the combining .unit output. The tone keyer is so arranged that the output energy from the combining unit, when a heavy current flows therethrough, produces through a high potential drop in a resistor element connecting the common connected filaments of the push-pull connected amplifiers and the center pointof the transformer secondary, to the primary of which the tone frequency generated in the tone generator 285 is supplied, so that a large current flowing in the plate circuit of the combining unit 28l tends to block the tubes of the tone keyer. 'The output of the tone keyer is directed through lines 281, 281 to an amplifier unit 288 which may be closely adjacent the tone keyer or remotely separated therefrom, if land lines are used to convey the signals from the tone keyer 283 to an amplifying unit 288 which is geographically separated from the tone keyer. The output energy from the amplifier 288 is directed through rectifier 2M to control the photoradio recording device 298 so as to reproduce the transmitted subject matter. This photoradio recording device maybe of any suitable and well known type, for example, a device of the type disclosed by Richard Howland Ranger and constructed substantially in accordance with the teachings in U. S. Patent #l,803,133, granted April 28, 1931, although any other and suitable ,type of recording unit may be substituted where desired.

The invention as herein described does not refer to the application of the system for television transmission wherein there is no direct recording action at the point of reception but rather the image production is merely the production of visual images in contrast to real images such as are produced by actual markings. Nevertheless, it should be understood that the broad principle of the invention as herein set forth and defined is applicable to television as well as to the transmission of still pictures, and therefore throughout the claims defining our invention in its broadest terms the word "pictures should be construed also as being capable of covering and relating to television transmission and reception of pictures. I I

,While only a single form of the invention has been shown and described herein, it is nevertheless to be understood that the broad principle covered by the invention is capable of many modifications and changes, and therefore we believe ourselves to be entitled to make and use all of these modifications which suggest themselves to anyone skilled in the art to which the invention is directed so long as such modifications and changes fall fairly within the spirit and scope of the invention as defined by the hereinafter. appended claims, wherein we claim and desire to secure by Letters Patent the following:

1. In the method of reproducing pictures or the like the steps which comprise electronically converting amplitude modulated carrier wave picture signalling impulses into rectified filtered energy and converting the rectified energy into constant amplitude constant frequency impulses and prolonging the duration of each impulse occurring at constant frequency for a time period directlyproportionate to the variations in amplitude of the picture signals.

2. The method of electrically reproducing half tone prints from a record surface which comprises electronically converting changes in light intensity on elemental areas of the subject into amplitude modulated carrier wave signals converting the carrier wave signals into rectified filtered energy, and changing the amplitude variations oi. the rectified energy 'into signalling pulsations of constant frequencyand amplitude each of a variable time duration directly proportionate to the amplitude of the picture signals. a

3. The method of electrically reproducing half tone prints from a record surface which comprises electronically converting changes in light tom recordings from a record surface which intensity on elemental areas of the subiect into amplitude modulated carrier wave signals converting the carrier wave signals into rectified filtered energy, and changing the amplitude variations of the rectified energy into signalling pulsations of constant frequency constant amplitude and variable-time duration directly proportionate to the amplitude of the original signals.

4. In the method of reproducing pictures or the like the steps which comprise electronically,

converting amplitude modulated carrier wave picture signalling impulses into rectified filtered energy-and converting the rectified energy into constant amplitude constant frequency impulses, prolonging the duration of each impulse occurring at constant frequency for a time period directly proportionate to the variations in amplitude of the original signals, and keying a transmitter by said constant amplitude constant frequency variable duration signals.

5. The method of electrically reproducing half tone recordings from a record surface which comprises converting changes in light intensity upon elemental areas of the record subject into signalling impulses of varying amplitudes of carrier wave energy proportionate to the changes in light intensity, electronically producing from the varying amplitude signalling impulses rectified filtered energy, electronically converting the rectified energy into constant amplitude constant frequency impulses and causing each produced impulse occurring at constant frequency to continue for variable time durations directly proportional to the amplitude of the varying amplitude picture produced signals.

6. The method of electrically reproducing half tone recordings from a record surface which comprises converting changes in light intensity upon elemental areas of the record subject into portional to the'amplltude of the varying amplitude signals produced, and keying a carrier frequency on and off completely from said constant frequency constant amplitude and variable duration signalling impulses.

'7. The method of electrically reproducing half comprises converting changes in light intensity upon elemental areas of the record subject into signalling impulses of varying amplitudes of carrier. wave energy proportionate to thechanges in light intensity. electronically producing from the varying amplitude signalling impulses rectified filtered energy. electronically converting the rectified energy into constant amplitude constant frequency impulses and causing each produced impulse occurring at constant frequency to continue for variable time durations directly proportional to the amplitude of the varying amplitude signals produced.

8. Themethod of electrically reproducing pictures which comprises producing constant frequency variable amplitude carrier wave electrical energy in which the amplitude variation is a function of the varying intensities of light and shadow on elemental areas of the record of which an image is to be reproduced, independently producing a screen frequency of'predetermined value and constant amplitude, rectifying the constant frequency variable amplitude picture signals. filtering the rectified signals. combining the rectified filtered picture impulses with the constant amplitude constant frequency screen frequency impulses, and producing electronically from the combined signals a series of constant frequency constant amplitude signals each of a width directly proportional to the variations in amplitude of the amplitude varying signals.

9. The method of electrically reproducing pictures which comprises producing constant frequency variable amplitude electrical energy in which the amplitude variation is a function of the varying intensities of light and shadow on elemental areas of the record of which an image is to be reproduced. independently producing a screen frequency of predetermined value and constant amplitude, rectifying the constant frequency variable amplitude picture signals. combining the rectified picture impulses with the constant amplitude constant frequency screenfrequency impulses, producing from the'combinod signals a series of constant frequency constant amplitude signals each of a width proportionate to the variations in amplitude of the amplitude varying signals, and cyclically shifting the phase of the screen frequency through 180 electrical degrees to change cyclically the position of the marking impulses with the spacing periods.

10. The method of electrically reproducing pictures which comprises producing constant frequency variable amplitude electrical energy in which the amplitude variation is a function of the varying intensities of light and shadow on elemental areas of the record of which an image is to be reproduced. independently producing a screen frequency of predetermined value and constant amplitude, rectifying the amplitude control ed signalling impulsesgcombiningthe the carrier'frequency during the spacing periods between said constant frequency constant amplitude pulsations. and periodically changing. at predetermined time periods. the phase of the screen frequency to change cyclically the position of the marking with the spacing.

11. The method of electrically reproducing pictures which comprises producing constant frequency variable amplitude electrical energy in whichthe amplitude variation is a function of the varying intensities of light and shadow on elemental areas of the record of which an image is to be reproduced, independently producing a screen frequency of predetermined value and constant amplitude, combining the constant frequency variable amplitude signalling impulses with the constant amplitude constant frequency screen frequency impulses, producing from the combined signals a series of constant frequency constant amplitude signals each of a width proportionate to the variations in amplitude of the 5 amplitude varying signals, generating a carrier stant frequency pulsations are produced and to interrupt the carrier frequency during the spacing periods between said constant frequency constant amplitude pulsations, and changing, after predetermined periods, the phase of the screen 16 frequency through an angle of substantially 180 to cyclically change the position of the marking pulses with the spacing.

12. In a system for electrically reproducing picture records, means for converting the vary- 20ing intensities of light and shadow on elemental areas of the subject of which an imageis to be reproduced into a train of amplitude varying carrier wave signals, means for rectifying the amplitude varying carrier wave signals, means to filter the rectified signals, spaced discharge means for converting the rectified filtered signals into electrical energy of constant amplitude and constant frequency, and means for controlling the time duration of the produced constant frequency constant amplitude signals in such mannerthat the signal is produced for a time period between each point of recurrence of the signal in direct proportion to the amplitude variation in the original signal.

13. In a system for electrically reproducing picture records, means for converting the varying intensities of light and shadow on elemental areas of the subject of which an image is to be reproduced into a train of amplitude varying signals, means for converting the amplitude varying signals into electrical energy of constant amplitude and constant frequency, means for controlling the time duration of the produced constant frequency constant amplitude signals 5 in such manner that the signal is produced for a time periodibetween each point of recurrence of the signal proportionate to the amplitude variation in the original signal, and means to cyclically interchange the signalling and spacing periods.

14. In a system for reproducing picture records, means for converting varying intensities of light and shadow on a record surface into amplitude varying. electrical energy, means for modulating a tone frequency in accordance with said amplitude variations, means for producing a screen frequency of fixed relation to the scanning speed for determining the detail in the reproduced picture, means for rectifying the amplitude modulated tone frequency for producing pulsating direct current of amplitude proportionate to the picture modulation, means for combining the screen frequency with the pulsatducing from said combined signal energy a wave train of energy of constant frequency and constant amplitude with a duration of signalling portions directly proportional to the amplitude of the amplitude varying signals, means for generating a carrier frequency, and means for keying said carrier frequency for transmission by said constant frequency constant amplitude varying duration signals, whereby for marking pe- 75 riods the carrier frequency is transmitted coning direct current, thermionic means for protinuously at full amplitude and for spacing pe- 'riods the carrier frequency-is interrupted.

15. In a system for reproducing picture records, means for converting at a predetermined rate the varying intensities of light and shadow on a record surface into amplitude varying electrical ener y, means for modulating a tone frequency in accordance with said amplitude variations, means for producing a screen frequency of fixed frequency relation to the rate of scanning for determining the detail in the reproduced picture, means for producing from said amplitude varying picture signal frequencies pulsating direct currents, means for combining the screen frequency with said pulsating direct currents, and thermionic means for producing from said combined signal energy a wave train of energy of constant frequency and constarit amplitude with a duration of signalling. portions directly proportional to the amplitude of the amplitude varying signals.

16. In a system for reproducing picture records, means for converting at a predetermined rate the varying intensities of light and shadow on a record surface into amplitude varying electrical energy, means for modulating a tone frequency in accordance with said amplitude variations, meansjfor producing a screen frequency of fixed frequency relation to the rate of scanning for determining-the detail in the reproducedpicture. means for producing from said amplitude varying picture signal frequencies pulsating direct currents. means for combining the'screen frequency with said pulsating direct currents, electrical means for producing from said combined signal energy a wave train of energy of constant frequency and constant amplitude with a duration of signalling portions directly proportional to the amplitude of the amplitude varying signals, means for generating a carrier frequency, and means for keying said carrier frequency for transmission by said-constant frequency constant amplitude varying duration signals, whereby for marking periods the carrier frequency is transmitted continuously at full amplitude and for spacing periods the carrier frequency is interrupted.

17. In a system for reproducing picture records, means for converting at a predetermined rate the varying intensities of light and shadow on a record surface into amplitude varying electrical energy, means for modulating a tone frequency in accordance with said amplitude variations, means" for producing a screen frequency of fixed frequency relation to the rate of scanning for determiningv the detail in the reproduced picture, means for producing from said amplitude varying picture signal frequencies terrupted, and a double setting means for cyclically changing the phase of the screen frequency through 180 to produce a cyclic change in the i 'a, oea',a4s' q 9 position of marking and spacing'indications to discharge means for converting the rectified iilprevent a direct alignment of adjacent marking" indications in the reproduced record.

. 18. In a system for electrically reproducing pictui'e records, means for converting the vary,

ing intensities of light and shadow; on successive elemental areas of the subject of which an" image is to-be reproduced into a train of amplitude varying carrier waveq signals, -means tered signals into electrical ener y of t amplitude and constant frequency, and means for controlling the time period of separationbetween each signal-pulse Offll series oi! constant frequency impulses in direct proportion to" the amplitude of the amplitude varyi signals. g

' HENRY'SHORE.

' signals. means to filter the rectified signals, space 10 ,!or rectifying the amplitude varying carrier wave JAMES N. WHITAKER. i0 

